Bumping gaia.json for 2 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/e606978d2b2e
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #12757 from etiennesegonzac/bug-924479-better-utility-tray-physics

Bug 924479 - Better Utility Tray physics r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/cbdc2a21ee61
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Bug 924479 - Better Utility Tray physics